With the popularity of display terminals, there is an increasingly high requirement for display devices. On the one hand, it is required that the display device has a compact structure and a good portability. On the other hand, it is required that the display device can have a larger display size when providing an entertainment service. However, the two requirements are mutual restraint. If a display device has a good portability, a screen size thereof should be reduced inevitably, and an entertainment experience of a user would be suffered. If a display device has a larger display screen, the size thereof should be increased inevitably, and the portability thereof would be suffered. The appearance of flexible screen provides possibility for solving the aforesaid technical problem. Since the flexible screen does not have rigidity, a certain mechanical structure is needed to support and guide the bending of the flexible screen. With respect to most flexible display devices, the whole screen can be hidden in the display device after folding once. When daily events need to be dealt with, such as watching weather report or time, answering the phone, the display device should be unfolded and then folded again. The unnecessary bending of the flexible screen is increased, and a lifetime thereof would be shortened. Due to the requirement of portability, the screen size of the display device with once-folding function is limited. With respect to a display device which can be folded for several times, a total thickness thereof would be increased, and the portability thereof would be suffered accordingly. Therefore, a display device which has a good portability, a long lifetime, and a large size display screen is needed.